The inspiration arrived in a haze at a Paul McCartney concert a few years ago in San Francisco.

"People in front of me started lighting up and then other people started lighting up," says Matthew Springer, a biologist and professor in the division of cardiology at the University of California, San Francisco. "And for a few naive split seconds I was thinking to myself, 'Hey, they can't smoke in AT&T Park! I'm sure that's not allowed.' And then I realized that it was all marijuana."

Last week, when #firingFriday was trending on Twitter and White House aides had to be reassured by the chief of staff that no changes were imminent, President Trump embraced the uncertainty in public statements. His willingness to say "you're fired" to so many people, so early in his administration is just another way Trump is unlike those who have come before him.

Vladimir Putin won a landslide election victory on Sunday — the fourth anniversary of the annexation of Crimea — extending his presidency by another six years as he easily breezed past a field of minor candidates left by the disqualification of his only credible rival.

If Putin serves to the end of his new fourth term, which expires in 2024, he would become the longest-serving leader of Russia since Soviet dictator Josef Stalin.